- Extracted `structuredCloneJSON()` utility to centralized package for consistent deep cloning with JSON fallback.
- Consolidated duplicate cloning logic across openai-responses, openai-responses-shared, and validation modules.
- Added resilience to message cloning in extension runner with try-catch fallback for non-cloneable objects.
- Optimized context emission in extension runner by skipping message cloning when no handlers exist.
- Added optional `contentIndex` field to AssistantMessageEvent variants for type consistency.